Diagnostic port plug



FIG. 1 is a front view of a diagnostic port plug showing my new design;

FIG. 2 is a left side view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a front-left angled isometric view thereof;

FIG. 6 is a rear-right angled isometric view thereof;

FIG. 7 is a top plan view thereof; and,

FIG. 8 is a bottom plan view thereof. 

CLAIM The ornamental design for a diagnostic port plug, as shown and described. 